1. Field of the Invention
The present invention relates generally to a power testing apparatus, and more specifically, to such a power testing apparatus that can brake rotation of a flywheel means independently of braking a rotation shaft thereof.
2. Description of the Background Art
In a power testing apparatus, a dynamometer and a tested object are drivingly coupled with each other in a direct or indirect manner for driving the dynamometer by the tested object or driving the tested object by the dynamometer to measure an output power of the tested object, a rotational resistance of the tested object, and so forth.
In one type of the power testing apparatus, such as a chassis dynamometer for testing vehicular engine performance or the like, driving wheels of a vehicle to be tested are placed on a pair of rollers which are coupled to each other with a common rotation shaft. An electric dynamometer has a rotation shaft which is drivingly connected to one end of the common shaft of the rollers through a coupling for co-rotation therewith. A rotation shaft of a flywheel unit is further coupled with another end of the common shaft of the rollers through a coupling for co-rotation therewith. In general, the flywheel unit includes fixed flywheels and adjusting flywheels. The fixed flywheels apply a predetermined inertial load to the tested object all through the power testing. On the other hand, each of the adjusting flywheels selectively applies a inertial load to the tested object through a clutch according to a required mode of the power testing.
As is known, when testing acceleration performance or climbing performance of the tested vehicle, a body weight, i.e. inertial mass of the vehicle is a decisive factor for measuring the respective performance. In the chassis dynamometer power testing, however, since the tested vehicle does not move relative to the power testing apparatus, the body weight does not directly become a driving load, i.e. an inertial load against the operation of a vehicular engine. Accordingly, the flywheel unit is provided for forming an actual engine load simulated inertial load which is variable according to the required simulation mode of the power testing.
In a practical use of the power testing apparatus as described above, the clutches are first set to engage so as to drivingly connect the adjusting flywheels to the rotation shaft of the flywheel unit. Accordingly, the engine load simulated inertial loads are fully applied to the tested vehicle. Subsequently, the clutches are set to disengage one by one for reducing the inertial load applied to the tested vehicle, which is required for smooth operation of the clutch, i.e. the disengagement of the clutch is easily performed even with the rotation shaft of the flywheel unit and the adjusting flywheel being rotated. Accordingly, the reducing of the inertial load applied to the tested vehicle can be performed while the power testing is being made. On the other hand, the engagement of the clutch in the same condition is undesirable due to a possibility of the clutch to be damaged, particularly in case of a toothed clutch being utilized. Accordingly, in the practical use of the power testing apparatus, as noted above, the clutches are engaged when starting the power testing, which are then disengaged one by one while the power testing is being made. As appreciated, the disengaged flywheels continue to rotate idle, which raises a problem.
When a series of the power test is finished, the rotation shafts of the dynamometer, the rollers and the flywheel unit are braked together by means of a disc brake to stop their rotation for replacing the tested vehicle with a new vehicle to be tested. As noted above, when starting another power test, the adjusting flywheels are coupled to the rotation shaft of the flywheel unit through the clutches.
It is to be appreciated that since each adjusting flywheel is supported on the rotation shaft of the flywheel unit through a roller bearing having a very small rotational resistance and the inertial mass of each adjusting flywheel is set considerably large, each flywheel continues to rotate idly about the rotation shaft of the flywheel unit unlimitedly with no external force applied thereto. Accordingly, it has been likely to happen that when starting the power testing for the new vehicle with the rotation shafts being stopped, the adjusting flywheels are still rotating idly. As mentioned above, the engagement of the clutch, while there is a difference in speed between the rotation shaft of the flywheel unit and the adjusting flywheel, is undesirable due to the possibility of the clutch being damaged. Accordingly, it is inevitably required to halt the power testing for the new vehicle until all the adjusting flywheels finish their rotation, resulting in prolongation of the power testing time.